Bulk bags are becoming increasingly popular for the purpose of transporting commodities that range from mined ores and minerals, in either granular or lumpy form, to agricultural products, chemicals, small hardware components and small packages of many different small products.
For the purpose of stacking filled bulk bags into transport containers it is generally advantageous to move the filled bags using a forklift truck. It has long been realised that lifting a filled bulk bag from the top restricts the height to which bags can be stacked in a transport container because of the restriction imposed by the roof of the container.
As a result, many different proposals have been made to provide a pair of laterally spaced, effectively rigid tubular elements at the bottom of a bag that are configured to receive the tines of a forklift truck so that lifting can take place from the bottom of the bag. This enables a filled bulk bag to be lifted almost to roof height within a transport container.
The earliest proposal of this nature known to applicant is European patent publication number EP 0080126 to Norsk Hydro AS wherein a pair of spaced tubular battens, that could be a plastic pipe or the like, are positioned between two layers of a bottom to the bag.
U.S. Pat. No. 5,785,175 proposes a bulk bag with a base that is configured to receive the tines of a forklift truck, many different configurations of base being disclosed. These bases occupy volume with a corresponding decrease in available space for load and would also be rather costly to manufacture as they must be rather strong.
British patent GB 2,161,452 discloses an arrangement in which tubular elements in the form of box sectioned reinforcing members are provided for receiving the forklift tines, one variation of which is made of wooden planks and slats with an alternative proposal being a plastics extrusion. Timber is costly; very much out of fashion; and even not accepted in some destinations, unless properly treated. Extrusions would have to be rather robust to withstand the substantial transverse forces imposed on them and extrusion of a tubular element does not allow for reinforcing ribs to be formed transverse to the length of the element.
U.S. Pat. Nos. 6,213,305 and 6,467,625 and corresponding publications disclose a number of different bulk bags having flexible sleeves depending from the bottom of the bag for accommodating forklift tine receiving members. One of the problems addressed by these patents is maintaining the so-called receiving members (that applicant terms tubular elements) within the flexible sleeves and various possibilities are put forward that are based on either elastic regions to the sleeves, typically at the entrances to the sleeves, or involve the clipping of two extrusions together with parts of the sleeves being clamped between the two parts.
Elastic entrances to the sleeves effectively narrow the entrances to the receiving members and make it more difficult for a forklift truck driver to align the free ends of the tines with the openings. This, accordingly, increases the already present possibility that the side of the bag immediately adjacent the entrance to such a tubular element may be damaged by the tines of the forklift truck during attempts to align the tines with the interior of the tubular element. Also, the alternative constructions, namely a pair of cooperating clipping extrusions, are expensive; relatively complicated; and also suffer from the disadvantage that reinforcing ribs transverse to the length of the extrusions cannot be easily formed. The alternative of injection moulding such components is also extremely expensive with die-costs for such large items generally being substantial. Still further, the positioning of the receiving members beneath the bottom of the bag means that they need to be stronger in view of the added weight exerted on them by this configuration, in use.